Recent years have witnessed the popularization of information systems and their widespread use in a variety of regions. Work that has conventionally been performed manually is also currently coming to be replaced by information systems and the amount of processing that such information systems are expected to accomplish has also reached huge proportions. As a result, the processing which information processing systems are tasked with cannot be completed within the desired time.
Therefore PTL1 discloses a technology for important application programs (hereinafter application programs are referred to simply as applications) whereby data which is used by the applications is arranged in file units in storage devices provided with suitable I/O performance. PTL1 enables the processing to be completed within the target time at least for high priority applications. Here, a technology will be described hereinbelow that is referred to as tiered storage control and whereby, if storage devices comprise storage areas exhibiting a plurality of different characteristics (I/O performance and reliability and the like), the storage areas each being referred to as tiered storage, the data used by a computer system is placed in any of the plurality of tiered storage.
Furthermore, in PTL2, data which a storage device writes to a virtual storage area in the device is divided into fragments which are smaller than files or the like which are then arranged in designated tiered storage. Further, PTL2 discloses a technology whereby, after the data is arranged in designated tiered storage, the storage device re-arranges the fragments in the tiered storage with a suitable I/O performance depending on the frequency with which a host computer accesses the fragments. PTL2 enables the arrangement, in typically costly high I/O performance tiered storage (known as upper tiered storage), only of data requiring such performance, thereby diminishing the usage of such costly upper tiered storage, and hence a performance similar to the I/O performance of the upper tiered storage can be expected.